1. Field of the Invention
The present invention relates to the field of wastewater treatment. More particularly, the invention is concerned with a process for reducing nitrogen-based and phosphorous-based nutrients in wastewater treatment effluent.
2. Description of the Prior Art
The design focus of prior art wastewater treatment plants has been to oxidize biosolids as measured by biochemical oxygen demand (BOD) and to clarify the effluent of particulates. In general, prior art treatment processes have not emphasized the removal of nitrogen-based and phosphorous-based nutrients from the clarified effluent. When the nutrient-rich effluent enters rivers, lakes and streams, water plant growth can be profuse, depleting the water of oxygen below levels needed to sustain desirable populations of fish and other aquatic life. Moreover, typical wastewater treatment reduces alkalinity when ammonia is oxidized to nitrate during aeration. Alkalinity is consumed and carbonic acid produced thereby lowering the pH of the effluent. As a result of these prior art processes, eutrophication of rivers, lakes and streams by the nutrient-rich effluent has become a major concern.
Prior art techniques for removing nitrogen and phosphorous compounds from wastewater have either been ineffective or too expensive. For example, effective wastewater denitrification requires nitrification of ammonia in an oxic environment followed by reduction of nitrate in an anoxic environment. Some prior art techniques have allowed contamination from one process to another and others have not maintained the required conditions long enough for effective treatment. Another prior art process uses methanol as a food source during denitrification. The methanol addition can be expensive and further requires subsequent processing to remove residual methanol. Other prior art techniques for the removal of phosphorous use chemical precipitation which is also an expensive process.